The phrase "are relatively rarely" is not correct in standard English usage.
It can be used when discussing the infrequency of an occurrence, but the adverb "rarely" should not be used with "relatively" in this context.
Example: "These species are relatively uncommon in this region."
Alternatives: "are quite uncommon" or "are fairly infrequent."
AR-15-style rifles are popular with gun enthusiasts but are relatively rarely used in gun homicides.
That's why mandatory-sentencing rules can affect the justice system even if the mandatory minimums are relatively rarely enforced.
Christian authors are relatively rarely quoted; excerpts from Aristotle and his commentators, a multitude of Greek and Roman authors, Arabic and more or less obscure medieval scientists are on the contrary extremely numerous.
But the focus of this summer's festival was on two European composers who are relatively rarely heard in this country, the German Helmut Lachenmann (born in 1935) and the Italian Marco Stroppa (born in 1959).
It is likely that states with P<∼0.001 are relatively rarely observed during the DMD simulation and subject to stochastic errors of estimate.
Mitochondrial disease mutations were not expected in the mtAncestor-1 and mtAncestor-2 sequences because they are relatively rarely found in population studies of modern humans and have potentially low individual survival.
In glossing the season, Mr. Kellogg said that "Patience" was relatively rarely done.
In the years since, his plays – more than 45 so far – have premiered more often abroad than at home, and even his early work is relatively rarely staged.
Compared with other late-industrial societies, Britain is relatively rarely plagued by firearms offenses, and when perpetrated they're often woefully inexpert.
The performance of the burners has a huge effect on furnace operation and efficiency, yet it is relatively rarely that burner design is fully integrated with the furnace heat transfer requirements; little wonder then that poor performance is often the result.
